1. Technical Field
The present disclosure relates to an object of small dimensions (on the order of one centimeter) containing electronic circuits powered by a cell. It more specifically relates to such an object containing a rechargeable cell having a non-negligible power consumption, the cell having to be able to provide an energy greater than 8 milliamperes-hour to offer 12 hours of autonomy. The present disclosure especially applies to in-the-ear hearing aids.
2. Discussion of the Related Art
The general appearance of an in-the-ear hearing aid is illustrated in FIG. 1. Such a hearing aid has an anatomic shape capable of being inserted in the external auditory canal. Generally, hearing aid 1 comprises a substantially planar surface 3 which, once the hearing aid has been inserted into the auditory canal, faces outwards. Preferably, for aesthetic reasons, the hearing aid is sized to avoid substantially protruding from the auditory canal. Such a hearing aid contains various electronic circuits for receiving, amplifying, adapting, and retransmitting sound signals, adapted to the hearing impairment which is desired to be overcome. Such electronic circuits have to be powered. Accordingly, a cell 5, inserted on the side of surface 3 in a cavity closed by a shutter 7, is provided.
An in-the-ear hearing aid has small dimensions. Calling H its largest dimension such as indicated in FIG. 1, conventional values of H range between 12 and 18 mm. The largest lateral dimension L approximately ranges from 8 to 12 mm. As a result, only cells of small dimensions may be inserted in such a device, for example a cell having a diameter ranging between 4 and 8 mm for a height ranging between 2 and 5 mm, for example, a cell having a 5.5-mm diameter and a 4-mm height. Further, such hearing aids have a relatively high power consumption, greater than 0.5 milliamperes in average, that is, in practice, with non-rechargeable cells, an autonomy on the order of one week at best can be reached, which results in a very high cell replacement cost. Further, when a rechargeable cell is used, the device power consumption results in that, with a rechargeable cell having the above-indicated dimensions, a recharge has to be provided practically every night. Thus, a user who would nevertheless like to use a rechargeable cell should, every day (against once a week for a disposable cell), perform a cell removal operation, an operation of recharge thereof, and an operation of putting back the cell in place. Given the small cell dimensions, these operations are delicate, and this all the more as persons using a hearing aid often are elderly people having a limited visual acuity and dexterity. Mechanical devices for grabbing the cell, placing it on a charger, and putting it back in place have thus been provided. Such devices are, however, not always very easy to use, especially for elderly people. Further, such operations cause a fouling of electric contacts.
This problem of handling a small rechargeable cell is posed for hearing aids such as indicated hereabove, but also for many other devices of small dimensions with a relatively high power consumption, such as swallowable cells that may correspond to pills having a diameter approximately ranging from 6 to 8 mm, and generally for any device which is desired to be tight.
It should be noted that the above-mentioned problem of frequent change or of frequent recharge of cells of small dimensions is not posed for devices such as watches which have a very low power consumption and for which the lifetime of a cell may approximately range from 1 to 5 years. On the other hand, this problem is not posed either for devices of relatively large dimensions, such as watches or devices having the format of a credit card, for which a surface area is available, which is sufficient to have charge coils of relatively large diameter (several centimeters), which, despite a generally poor coupling with a primary, enable to provide a sufficient power due to their number of turns and to their diameter.
There thus is a need for an electric object provided with a rechargeable cell which does not need being extracted from the object in order to be recharged.